This invention relates to an internal combustion engine and more particularly to a crankcase ventilating system for internal combustion engines.
In order to reduce the emission of unwanted hydrocarbons and other combustible material to the atmosphere from internal combustion engines, it has been the practice to ventilate the crankcase of the engine by the blow-by gases that pass across the piston rings and into the crankcase chamber. These blow-by gases are then collected and returned by a crankcase ventilating system that normally utilizes a positive crankcase ventilating (PCV) valve to the induction system of the engine. Thus these gases are returned to the combustion chamber and further combustion of the undesirable constituents occurs.
A problem with this type of positive crankcase ventilating system is that when the gases are returned to the induction system and under low ambient temperatures, not only is the induction system but the entire engine at a relatively low temperature, particularly when it is initially started. Since the ventilating gases also include a fair amount of water vapor, they can not only condense but also can solidify in the crankcase ventilating conduit and cause significant problems.
This problem may be best understood by reference to FIG. 1, which is a partial cross sectional view showing the conventional type of crankcase ventilating system. The engine, indicated generally by the reference numeral 11, is provided with an internal crankcase ventilating system which includes an arrangement for returning blow-by gases to an area such as the valve cover 12 which is provided with an oil separator, shown partially at 13, for returning lubricant to the crankcase. The gases exist the cam chamber enclosed by the cam cover 12 through a first metallic fitting 14 onto which one end of a flexible hose 15 is positioned. The opposite end of the flexible hose 15 is connected to a further fitting 16, which communicates with the interior of an air inlet device 17 that collects atmospheric air for delivery to the engine combustion chambers.
Because of the aforenoted problems in connection with condensation and freezing, an insulating sleeve 18 frequently is employed encircling the flexible conduit 15 in the area between the metallic fittings 14 and 16. In spite of this insulation, water vapor in the blow-by gases, which flow in the direction of the arrow shown in this figure, can condense particularly in the area where the fitting 16 joins the air inlet device 17. Thus, ice particles indicated at 19 can form in this area and either restrict or in extreme cases totally cut off the re-circulating air flow. Various arrangements have been proposed for attempting to avoid this problem, but they have not been totally effective and in many instances can be expensive.
It is, therefore, a principle object to this invention to provide an improved crankcase ventilating system for an internal combustion engine.
It is a specific object to this invention to provide a simple and effective heat insulating arrangement for connecting the crankcase ventilating tube to the induction system of the engine that will provide adequate insulation to preclude the likelihood of freezing even under extremely low ambient temperatures.
This invention is adapted to be embodied in an internal combustion engine and crankcase ventilating system therefore. The engine includes an induction system for collecting atmospheric air and delivering the collected air to at least one combustion chamber of the engine. A crankcase ventilating system collects and exhausts blow-by gases from the engine and returns them to the combustion chamber through the induction system for reducing undesirable emissions to the atmospheric. This crankcase ventilating system communicates with the induction system through a fitting having a double wall construction comprised of an inner tube received in an outer tube with the outer wall of the inner tube being circumferentially spaced from the inner wall of the outer tube for heat insulation of the blow gases and inner tube.